Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2001-03-23
2002-09-10
Sanders, Kriellion A. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S086000, C524S297000, C524S398000, C524S403000, C524S450000, C524S492000
Reexamination Certificate
active
06448306
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to certain non-silicone vulcanized rubber articles made from at least a majority by weight of nitrile butadiene rubber and/or natural rubber that include silver-based compounds to provide highly desirable long-term antimicrobial characteristics within the cured rubber articles. Such articles are in either solid or blown (foam or sponge) state (or combinations of both in multilayered forms) which can be utilized in a variety of different applications. As silver-based compounds are deleteriously affected by utilization of standard curing agents and curing accelerators, such as sulfur-based compounds and/or systems, the ability to provide such an effective antimicrobial vulcanized rubber article is rather difficult. However, this invention encompasses the presence of different non-sulfur-based curing systems and agents, such as peroxides, as one example, that permit vulcanization and do not irreversibly bind silver ions thereto, thereby resulting in long-term antimicrobial performance of the ultimate rubber article itself. The rubber articles must also comprise fillers and may also include plasticizers to provide desired characteristics of dimensional stability, stiffness, flexural modulus, tensile strength, abrasion resistance, elongation, and the like, for the ultimate rubber article, while simultaneously and surprisingly enhancing the antimicrobial efficacy of the rubber article as well.
DISCUSSION OF THE PRIOR ART
All U.S. Patents listed below are herein entirely incorporated by reference.
There has been a great deal of attention in recent years given to the hazards of bacterial contamination from potential everyday exposure. Noteworthy examples of such concerns include the fatal consequences of food poisoning due to certain strains of
Eschericia coli
being found within undercooked beef in fast food restaurants;
Salmonella enteritidis
contamination causing sicknesses from undercooked and unwashed poultry food products; and illnesses and skin infections attributed to
Staphylococcus aureus, Klebsiella pneumoniae,
yeast (
Candida albicans
), and other unicellular organisms. With such an increased consumer interest in this area, manufacturers have begun introducing antimicrobial agents within various everyday products and articles. For instance, certain brands of cutting boards, shoe soles, shoe inserts, medical devices and implements, liquid soaps, etc., all contain antimicrobial compounds. The most popular antimicrobial for such articles is triclosan. Although the incorporation of such a compound within liquid or certain polymeric media has been relatively simple, other substrates, specifically vulcanized rubber and surfaces thereof, have proven less accessible. Furthermore, such triclosan additives have proven to be difficult in use or ineffective for certain bacteria. For instance, triclosan itself migrates easily within and out of certain polymeric substrates and/or matrices (and thus is not very durable), lacks thermal stability, and does not provide a wide range of bacterial kill (for instance does not exhibit any kill for
Pseudomonas aeruginosa
).
Antimicrobial rubber formulations are certainly highly desired for the production of vulcanized rubber articles and compositions to provide not only antibacterial benefits, but also antifungal, antimildew, antistaining, and odor control properties. Rubber articles are utilized in many different applications, from automobiles (hoses, tires, bumpers, etc.), to household items (toys, sink washers, gaskets, appliances, floor mats, door mats, carpeted rubber mats, gloves, and the like), and other areas in which bacterial growth is a potential problem. There thus remains a long-felt need to provide an effective, durable, reliable antibacterial vulcanized rubber formulation which will provide such long-term antibacterial, etc., effects within the final vulcanized article. Unfortunately, such a highly desired antimicrobial rubber formulation and/or vulcanized article containing silver-based antimicrobial agents has heretofore not been provided by the pertinent prior art.
The closest art includes Japanese Patent Application 1997-342076 which discloses the production of unvulcanized rubber formulations and articles exhibiting antibacterial properties due to the presence of silver complexes. Such formulations are formed through high temperature kneading in an oxygen-free atmosphere and are used as parts in a water disinfection system. Again, no vulcanized rubber is taught or obtained within or through this disclosure. Antimicrobial rubber bands have been taught in Japanese Patent Application 1997-140034 in vulcanized form with silver antimicrobials therein. However, such compounds are rather limited in use and the vulcanization step must include a sulfur curing agent to effectuate the final vulcanized arrangement of the subject rubber. Such sulfur curing agents have a remarkably deleterious effect on certain silver-based antimicrobials such that the sulfur reacts with the silver ion to form silver sulfide, therby rendering it ineffective as a bactericide. As such, the utilization of such specific rubber band formulations for and within large-scale antimicrobial articles is basically unworkable.
Certain types of antimicrobial peroxide-catalyst vulcanized rubber formulations have been produced in the past; however, such peroxide-cured rubbers are all silicone-based. It is well understood and accepted that silicone rubbers cannot be vulcanized by typical sulfur-based catalysts. Thus, the antimicrobial rubber formulations of Japanese Patent Applications 1997-026273 and 1995-065149 as well as U.S. Pat. No. 5,466,726 are standard vulcanized silicone rubber formulations and articles which also include certain antimicrobial compounds.
Furthermore, rubber latexes (non-vulcanized) comprising antimicrobials have been disclosed (U.S. Pat. No. 5,736,591, for example), as have floor mats having silver-based antimicrobials incorporated within pile fiber components and which have non-antimicrobial rubber backings cured through peroxide-catalyzed vulcanization to protect the pile fiber antimicrobial compounds from attack by any sulfur compounds (as in Japanese Patent Applications 1993-3555168 and 1995-38991). Again, however, to date there have been no disclosures or suggestions of producing a vulcanized non-silicone rubber formulation exhibiting excellent antimicrobial properties through the long-term effective utilization of silver-based antibacterial compounds. This invention fills such a void.
OBJECT OF THE INVENTION
It is therefore an object of this invention to provide an antimicrobial vulcanized rubber-containing article, wherein said rubber is selected from the group consisting of nitrile butadiene rubber, natural rubber, and any mixtures thereof, wherein said article exhibits sufficient antimicrobial activity and structural integrity to withstand repeated use without losing an appreciable level of either antimicrobial power or modulus strength. Another object of the invention is to provide an antimicrobial vulcanized nitrile butadiene or natural rubber article comprising silver-based antimicrobial compounds which include curing agents which do not deleteriously effect the antimicrobial activity of the finished vulcanized nitrile butadiene or natural rubber article (and thus is essentially free from sulfur-based curing agents and accelerators). Yet another object of this invention is to provide a vulcanized nitrile butadiene or natural rubber-containing article that exhibits log kill rates for
Staphylococcus aureus
and
Klebsiella pneumoniae
(and/or other types of bacteria as well) of at least 1.0 after 24 hours exposure at room temperature as well as prevention of growth of certain fungi after at least 15 days of exposure. Still another object of this invention is to provide a vulcanized nitrile butadiene or natural rubber-containing article comprising structural integrity filler components and plasticizers (such as silica, metal salts, organic salts, pigments, such as carbon black, calcium c
Burke III William O.
Haas Geoffrey R.
Kerr Robert C.
Lever John G.
Patel Bhawan
Milliken & Company
Moyer Terry T.
Parks William S.
Sanders Kriellion A.
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